Enclosed electric arc lamp



Sept. 13, 1938. ELE 'ME S 2,130,304

ENCLOSED ELECTRIC ARC LAMB Filed Sept. 25. 1936 lnvnfior: Eugene Lemmefs, b I y A His ttorney Patented Sept. 13, 1938 Eugene Lemmers,

New York Cleveland, Ohio, assignor to -General Electric Company,

a corporation of Application September 25, I936, Serial No. 102,554

11 Claims.

This invention relates to electric discharge lamps generally and more particularly to high pressure metal vapor arc lamps and is a continuation in part of my application Serial No. 8,2

filed February 26, i935.

One of the objects of my invention is to provide a lamp which may be operated without additional equipment on constant current circuits such as are standard for street lighting in this country. Another object is to provide means for heating portions of the lamp which arenormally insufficiently heated. Another object is to so construct the lamp as to make the bulb as large as possible and still satisfy the other conditions of starting.

In order that a high pressure metal vapor lamp may function it must be so designed and operated that all parts of the inside of the lamp receive suiilcient heat to raise the vapor pressure to the operating condition. Those parts of'the lamp which receive heat from the discharge are very easily raised to the operating temperature since' the watts dissipated in the discharge rise as the lamp warms up no matter whether the lamp is operated in the conventional manner or on constant current. However, for those parts of the lamp which receive their heat from the electrodes, the amount of heat received is quite diiferent as be-: tween conventional operation and constant current operation. In conventional operation, the electrode wattage dissipation is quite high at the start, high enough to warm the lamp parts dependent upon this heat to a point where the total lamp watts produce enough heat to spread over to those parts and maintain the temperature as the watts in the electrodes taper off to the operating condition; However, when a lamp of conventional design is .operated at constant current, v

the electrode wattage, and thus the heat available, is at all times approximately constant and of comparatively low value. Because of this, the lamp parts dependentupon the electrodesfor most of their heat never get hot enough to raise the vapor pressure 'to a point where the total lamp watts'will spread enough heat to these parts to produce an operating condition. Therefore, in order that a lamp operate at constant current, the heat generated by the electrodes must be more efficiently transferred to the bulb walls. In lamps of moderate pressure, this may be done by making'the bulb very small or by locating the electrodes closer to the bulb parts that need the heat and by coating these parts of the bulb with anopaque material. However, this procedure, at least in lamps which operate at a pressure in ex? cess of one atmosphere, may cause a great deal of trouble in the form of cracked seals and blown out bulbs and rapid depreciation.

According to my invention, the above-mentioned difliculties are obviated by so shaping the elec- 5 trades and the envelope or bulb that as much as possible of the heat from the electrodes is directed toward the portions of the lamp which are normally insufficiently. heated. When this is done, s

the distance between the bulb and electrodes and 10 the size of the bulb necessary for successful oper--- ation at constant current is such that no diiilculty is'experienced. Further features and advantages of my invention will appear from the I following description of species thereof.- v

In the drawing, Fig. l is an elevation of a lamp comprising my invention; Fig. 2 is a section taken onthe line 2-2 of Fig. 1; and Figs. 3-5 are elevations of modified forms of the lamp.

Referring to Fig.1, the lamp comprises a cy- 20 lindrical envelope or bulb l0 having a rounded, approximately hemispherical, upper end, the lower end being tapered more sharply and being curved inwardly at H. Upper and lower electrodes l2 and i3 respectively are disposed in the vertical 25 axis of the bulb ill so that the positive column path therebetween is in the said vertical axis, the lower electrode being closer to the bottom of the bulb than the upper electrode is to the top of the bulb. Each of the electrodes It), I3 consists of a block l4 ofelectron emissive material which is secured, as by welding, to a thin disc ends of the bulb Ill. The lamp is also preferably 5 provided with an auxiliary starting electrode consisting of a wire i8 extending through the upper end of the bulb l0 adjacent to the upper electrode I2. The bulb III also contains a small quantity of vaporizable metal l9, preferably mercury, and 50 a filling of a rare gas, preferably argon, at a pressure at about 10 mm.

The lamp is preferably enclosed in a shield of .some'sort to protect it from drafts of airandto maintain the ambient temperature more nearly 5 iii of metal, preferably a refractory metal so as I being prefertlon of a stem tube 26 sealed to the upper end of the envelope 20, one end of said frame being connected to a lead 21 which extends to the base shell ,22. The upper lead It extends through an opening in a mica disc 28 mounted on the upper end of the frame 2| and is secured to a lead wire 29 which extends through the stem press 25 to the end contact 23 of the base 2|. The lower lead i1 is secured to the bottom of the frame 24. The starting electrode lead- I8 is connected through a high resistance 30 to the frame 24 at 3| (Fig. 2) and through said frame and lower lead I! to lowerelectrode i3. The bottom of the frame 24 is prevented from vibrating by a transverse curved spring member 32 (see Fig. 3) which engages opposite sides of the envelope wall and is'secur'ed to said frame by a wire 33. The outer envelope 20 may be open to the atmosphere or it may be filled with nitro-- gen at a pressure of one atmosphere or with a gas having high heat conductivity such as heliumor hydrogen.

The junction, at 34, of the side and lower end walls of the bulb Iii is preferably at or below the level of the upper end or are sustaining surface of the lower electrode block ll. When the said Junction 3| is above the upper end of said electrode block it, the arc tends to bow out toward the bulb wall during the operation of the lamp.

the conventional lamp without the said disc.

The disc it of the lower electrode ilradiates heat during the starting and operation of the lamp toward the bottom of the bulb which, with conventional types of electrodes, is not heated sufficiently to enable the lamp to be warmed up to operating condition on constant current circuits. The said disc II and the block are so proportioned that the wattage disipation at the electrodes will heat them to a temperature desirable for emcientemission of electrons. Only slightly less than half of thetotal heat radiated will be directed toward the bottom of the lamp where it is needed. The inwardly curved portion II at the bottom of the bulb also assists in maintaining a higher temperature at that point.

In the lamp shown in Fig. 3, the bottom of the bulb I0 is tapered a little more sharply and instead of being provided with an inwardly curved 'portion as in Fig. 1, it has a coating of heat throughout the bulb, thereby permitting operat- Such lamps may be ing at increased pressures. operated at pressures of about seven atmospheres with bulbs of ordinary thickness.

In Fig. 5, the lower end of the cylindrical bulb ii is more flattened than in Fig. 3. In order to properly heat the said lower end in this case, it is coated at 35, as in Fig. 3, and the disc I! of the lower electrode I3 is dish-shaped so as to radiate heat laterally to the walls of the lower end and V to the junction 34 of lower end and side walk.

The said lower disc I! may be dished upwardly instead of downwardly to produce substantially the same effect.

Lamps of the type shown in Fig. 3 have been made inlOO watt sizes. The bulbs II were of 25 mm. inside diameter and contained about .0055 cc. of mercury and a filling of argon at about 10 mm.- pressure. The blocks M of electron emissive material were about 3 mm. long and 3 mm. in diameter and the disc ii of the upper electrode "l2 was 13 mm. in diameter while the disc I! of the lower electrode l3 was 8 mm. in diameter. These lamps were operated on alternating current at '70 volts with a current of 1.6 amperes. The lamps operate with a concentrated are discharge between the electrodes at a pressure of about two atmospheres, which gives an advantage in efllciency over lower pr.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric discharge lamp of the high pressure metal vapor arc type adapted to be mounted with its longitudinal axis vertically disposed and comprising a bulb, a vaporizable metal in said bulb, upper and lower electrodes mounted substantially in the axis of said bulb adjacent the ends thereof, the lower electrode being closer to the bottom of the bulb than the upper electrode is to the top of the bulb, each of said electrodes comprising a metal disc disposed transversely of the axis of said bulb and adapted to radiate heat to the ends of said bulb during operation of the lamp.

2; An electric discharge lamp of the high pressure metal vapor arc type adapted to be mounted with its longitudinal axis vertically disposed and comprising a bulb, a vaporizable metal in said bulb, upper and lower electrodes mounted substantially in the axis of said bulb adjacent the ends thereof, the lower electrode being closer to the bottom of the bulb than the upper electrode is to the top of the bulb, each of said electrodes comprising a metal disc disposed transversely of the axis of said bulb and adapted to radiate heat to the ends of said bulb during operation of the lamp, the upper disc being of larger diameter than the lower disc to deflect the rising currents of hot vapor toward the sides of the bulb.

3. .An electric discharge lamp of the hi h pressure metal vapor arc type adapted to be mounted with its longitudinal axis vertically disposed and comprising a bulb, a vaporizable metal in said bulb, upper and lower electrodes mounted substantially in the axis of said bulb adjacent the ends thereof, the lower electrode being closer to the bottom of the bulb than the upper electrode is to the top of the bulb, each of said electrodes comprising a metal disc disposed transversely of the axis of said bulb and adapted to radiate heat to. the ends of said bulb during operation of the lamp, the lower disc being dished so as'to radiate heat laterally as well as downwardly.

4. An electric discharge lamp of the high pressure metal vapor arc type adapted to be mounted with-its longitudinal axis vertically disposed and comprising a substantially cylindrical bulb containing a quantity of vaporizaole metal, upper and lower electrodes mounted substantially in the axis of said bulb adjacent the ends thereof, the lower electrode being closer to the bottom of the bulb than the upper electrode is to the top of the bulb, each of saidelectrodcs comprising a metal disc disposed transversely of the axis of said bulb and adapted to radiate heat to the ends of said bulb during operation of the lamp. v

5. An electric discharge lamp adapted to be mounted with its longitudinal .axis vertically disposed and comprising a substantially cylindrical bulb having a rounded upper end and a tapering lower end, upper and. lower electrodes mounted substantially in the axis of said bulb adjacent the-ends thereof, the lower electrode being closer to the bottom of the bulb than the upper electrode is to the top of the bulb, each of said electrodes comprising a metal disc having an-electron emissive body secured thereto in intimate thermal contact, said disc being disposed transversely of the axis of said bulb and adapted to radiate heat to the ends of the bulb during operation of the lamp.

6. An electric discharge lamp adapted to be mounted with its longitudinal axis vertically disposed and comprising a substantially cylindrical bulb having a rounded upper end and a tapering lower end and upper and lower electrodes mounted substantially in the axis of said bulb adjacent the ends thereof, each of said electrodes comprising a metal disc disposed transversely of the axis of said bulb and adapted to radiate heat toward the ends of said bulb during operation of the lamp, the upper surface of said lower electrode being located within the cylindrical portion of said bulb.

7. An electric discharge lamp adapted to be mounted with its longitudinal axis vertically disposed and comprising a substantially cylindrical bulb having a-rounded upper end and a tapering lower end, a coating of heat reflecting material on the said tapering lower end of said bulb, and upper and lower electrodes mounted substantially in the axis of said bulb adjacent the endsthereof, each of said electrodes comprising a metal disc disposed transversely of the axis of said bulb and adapted to radiate heat toward the ends of said bulb during operation of the lamp,

the upper surface of said lower electrode being ljoflated within the cylindrical portion of said 8. An electric discharge lamp adapted to be mounted with its longitudinal axis vertically disposed and comprising a substantially cylindrical bulb having a rounded upper end and a tapering lower end and upper and lower electrodes mounted substantially in the axis of said bulb, adjacent the ends thereof, each of said electrodes comprising a metal disc disposed transversely of the axis of said bulb and adapted to radiate heat toward the ends of said bulb during operation of-the lamp, the upper surface of said lower electrode being located within the cylindrical portion of said bulb, the disc of said lower electrode being dished so as to radiate heat laterally as well as downwardly.

9. An electric discharge lamp adapted to be mounted with its longitudinal axis vertically disposed and comprising a substantially cylindrical bulb having a rounded upper end and a tapering lower end, a portion of said lower end of said bulb being curved inwardly, and upper and lower electrodes mounted substantially in the axis of said bulb adjacent the ends thereof, each of said electrodes comprising a metal disc disposed transversely of the axis of said bulb and adapted to radiate heat toward the ends of said bulb during operation of the lamp, the upper surface of said lower electrode being located within the cylindrical portion of said bulb.

10.. In an electric discharge lamp, a bulb con.- taining a pair of electrodes mounted substantially in the axis of said .bulb adjacent the ends thereof, each of said electrodes consisting of a block of electron emissive material mounted onv and making intimate thermal contact with a metal disc, said discs being disposed transversely of the axis of the bulb with the said blocks thereon facing each other, said discs being adapted to radiatev heat toward the ends of said bulb during operation of the-lamp. v

11. In an electric discharge lamp, a substantially cylindrical bulb containing a pair of electrodes mounted substantially in the axis of said bulb adjacent the ends thereof, each of said electrodes consisting of a block of electron emissive material mounted on and making intimate thermal contact with a metal disc, said discs being disposed transversely of the axis of the bulb with the said blocks thereon facing each other, said discs being adapted to radiate heat toward the ends of said bulb during operation of the lamp.

EUGglNE LEMMERS. 

